Condom use problems during anal sex among men who have sex with men (MSM): findings from the Safe in the City study.

Our research aims were to: (1) assess the prevalence of two condom use problems: breakage or slippage and partial use (delayed application or early removal) among men who have sex with men (MSM) seeking services in urban US STD clinics; and (2) examine the association between these condom use problems and participant, partner and partnership characteristics. Analysis was restricted to HIV-negative MSM who reported having anal sex at least once in the preceding 3 months and who completed both the baseline and 3 month follow-up assessments. Two models were fitted using the generalized estimating equations (GEE) approach. A total of 263 MSM (median age=32 years) reported 990 partnerships. Partnerships with no condom use 422 (42.6%) were excluded. Thus, 207 MSM and 568 partnerships were included. Among condom users, 100% use was reported within 454 partnerships (79.9%) and <100% within 114 (20.1%), and 21(3.7%) reported both condom use problems, 25 (4.4%) reported only breakage, 67 (11.8%) reported only partial use, and 455 (80.1%) reported no errors. The breakage or slippage and partial use rates per condom used were 3.4% and 11.2%, respectively. A significantly higher rate of breakage or slippage occurred among non-main partnerships. Characteristics associated with increased odds for condom breakage or slippage were: lower education level (OR=2.78; CI: 1.1-7.5), non-main partner status (OR=4.1; CI: 1.5-11.7), and drunk or high during sex (OR=2.0; CI: 1.1-3.8), and for partial use: lower education level (OR=2.6; CI: 1.0-6.6), perceived partner sexually transmitted infections (STI) risk (OR=2.4; CI: 1.3-4.2), and inconsistent condom use (OR=3.7; CI: 2.0-6.6). A high percentage of MSM partnerships reported no condom use and among condom users, a sizable proportion did not use them consistently or correctly. MSM may benefit from interventions designed to increase proficiency for condom use with a particular focus on the behaviors of inconsistent and partial condom use.

Optical dynamics of energy-transfer from a CdZnO quantum well to a proximal Ag nanostructure.

We studied photoluminescence (PL) and energy-transfer dynamics in a hybrid structure comprising a Cd(0.08)Zn(0.92)O quantum well (QW) and an Ag nanostructure. The observed PL quenching was dependent on the electronic states in the QW. Quenching occurred at low temperature where excited carriers recombined radiatively because of excitonic localization, which disappeared with increasing temperature due to delocalization of excitons. Furthermore, nanostructured Ag surfaces produced local surface plasmon (LSP) absorption that was resonant with the PL peak energy of the QW emission. These results indicate that the recombination energy of excitons transfers nonradiatively to induce LSP excitation, which was revealed using time-resolved PL measurements.

In situ real-time monitoring of changes in the surface roughness during nonadiabatic optical near-field etching.

We performed in situ real-time monitoring of the change in surface roughness during self-organized optical near-field etching. During near-field etching of a silica substrate, we detected the scattered light intensity from a continuum wave (CW) laser (lambda = 633 nm) in addition to the etching CW laser (lambda = 532 nm) light source. We discovered that near-field etching not only decreases surface roughness, but also increases the number of scatterers, as was confirmed by analyzing the AFM image. These approaches provide optimization criteria for the etching parameter and hence for further decreases in surface roughness.

Significant effect of linker sequence on DNA recognition by multi-zinc finger protein.

The unique linker sequence of the native nine zinc finger transcription factor IIIA (TFIIIA) appears to significantly affect its novel DNA recognition mode. An artificial new nine zinc finger peptide Sp1ZF9T has been created by connecting three units of the three zinc finger domains of Sp1 with the TFIIIA-type linker. The DNA-binding characteristics of Sp1ZF9T were evaluated by the gel mobility shift, DNase I footprinting, and methylation interference assays, and compared with those of the previous Sp1ZF9 with a Krüppel-type linker. The gel mobility shift assays revealed that Sp1ZF9T forms two complex species, a short-lived species (B-2) and a long-lived species (B-1), with GCIII DNA (5'-GGG GCG GGG GGG GCG GGG GGG GCG GGGCC-3'). The B-2 complex dissociated into the free peptide and DNA, whereas the B-1 complex was stable even after 72 h. The DNase I footprinting and methylation interference results indicated that 3'- and central portions of GCIII DNA are recognized by Sp1ZF9T in the B-1 complex. The present DNA binding mode of Sp1ZF9T is evidently different from that of Sp1ZF9. Namely, fingers 1-5 participate in the DNA contact of Sp1ZF9T, and fingers 1-9 in that of Sp1ZF9. Therefore, the linker sequence among the zinc finger domains has a significant effect on the specific DNA recognition by the multi-zinc finger proteins.

Multiconnection of identical zinc finger: implication for DNA binding affinity and unit modulation of the three zinc finger domain.

Cys(2)-His(2)-type zinc finger proteins have a tandemly repeated array structure consisting of independent finger modules. They are expected to elevate the DNA binding affinity and specificity by increasing the number of finger modules. To investigate the relation between the number and the DNA binding affinity of the zinc finger, we have designed the two- to four-finger peptides by connecting the central zinc finger (finger 2) of Sp1 with the canonical linker sequence, Thr-Gly-Glu-Lys-Pro. Gel mobility shift assays reveal that the cognate three- and four-finger peptides, Sp1(zf222) and Sp1(zf2222), strongly bind to the predicted target sequences, but the two-finger peptide, Sp1(zf22), does not. Of special interest is the fact that the dissociation constant for Sp1(zf2222) binding to the target DNA is comparable to that for Sp1(zf222). The methylation interference, DNase I and hydroxyl radical footprintings, and circular permutation analyses demonstrate that Sp1(zf2222) binds to its target site with three successive zinc fingers and the binding of the fourth zinc finger is inhibited by DNA bending induced by the binding of the three-finger domain. The present results strongly indicate that the zinc finger protein binds to DNA by the three-finger domain as one binding unit. In addition, this information provides the basis for the design of a novel multifinger protein with high affinity and specificity for long DNA sequences, such as chromosomal DNAs.